What it cost to engineer a marine alternator regulator
Total invested
$38,354
Sales to date
$1,511
Net loss
$36,843
Hours of my labor
4,314
Years
4.2
Hours per day
2.8
Where the money went
Show as a table
| Category | Amount | Share |
|---|---|---|
| Circuit boards, parts, and materials | $19,497 | 50.8% |
| Contract design help | $11,939 | 31.1% |
| Training and reference | $2,415 | 6.3% |
| Test equipment | $1,630 | 4.2% |
| AI development tools | $1,554 | 4.1% |
| Website, hosting, and software | $1,043 | 2.7% |
| Shipping, banking, and trade shows | $277 | 0.7% |
Spend by month
Itemized months only - March 2025 onward.
What a single XREG-010 costs to produce
| Item | Qty | Cost |
|---|---|---|
| Circuit board, landed | 1 | $75.21 |
| Cherry enclosure, Base and Wall Dock | 1 | $30.50 |
| Alternator current sensor, 300 A hall clamp | 1 | $12.90 |
| Digital temperature sensors, M4, M5, and M8 ring lug | 3 | $6.79 |
| Mounting hardware, stainless screws and UHMW washers | 7 + 3 | $2.39 |
| P and N alternator configuration jumper | 1 | $1.56 |
| Alternator current sensor mounting screws, 316 stainless for plywood and OSB | 2 | $0.57 |
| Neoprene foam strip, adhesive backed | 3 in | $0.53 |
| Heat-shrink labels for the four data cables | 4 | $0.08 |
| Printed instructions | 1 | $0.04 |
| Product cost per unit | $130.57 |
| Shipping prep labor, 30 minutes at $50 an hour | $25.00 | |
| Outbound postage, USPS Priority Mail with insurance | $17.00 | |
| Card and payment processing | $11.61 | |
| Delivered to a US customer | $184.18 | |
| Sale price | $390.00 | |
| Profit per unit sold | $205.82 | |
| Gross margin on the sale price | 52.8% | |
| Markup on delivered cost | 111.7% |
Engineering hours are not in these figures.
What the board costs, at a run of fifty
Show the run totals
| Line | Run $ | Per board $ |
|---|---|---|
| PCB fabrication | $98.64 | $1.97 |
| Assembly services | $378.26 | $7.57 |
| Components | $2,122.17 | $42.44 |
| DHL Express shipping to the USA | $290.13 | $5.80 |
| US import duty, 35% of declared value | $871.36 | $17.43 |
| All-in for 50 boards | $3,760.56 | $75.21 |
Where the component money goes, at a run of a hundred
Show as a table
| Function | Placements | Unique parts | $ per board | Share |
|---|---|---|---|---|
| Analog inputs, battery shunt, and engine RPM | 45 | 26 | $10.69 | 22.8% |
| Inertial sensor and barometer | 3 | 3 | $7.73 | 16.5% |
| Input power protection | 25 | 21 | $6.71 | 14.3% |
| NMEA 2000 | 11 | 11 | $4.94 | 10.5% |
| CPU and radio | 39 | 6 | $4.27 | 9.1% |
| Field drive | 21 | 17 | $3.56 | 7.6% |
| Power supplies | 38 | 15 | $2.91 | 6.2% |
| NMEA 0183 serial inputs | 7 | 4 | $2.58 | 5.5% |
| Connectors | 3 | 2 | $1.34 | 2.8% |
| Optocoupler digital inputs | 20 | 4 | $1.12 | 2.4% |
| Buzzer and status outputs | 14 | 12 | $0.61 | 1.3% |
| USB and programming | 15 | 9 | $0.44 | 0.9% |
| Temperature sensor bus | 3 | 3 | $0.08 | 0.2% |
| Total | 244 | 95 | $46.98 | 100% |
Each line carries its share of the assembler's flat $130.37 extended-part fee, $1.30 a board at 100 boards. The unique-parts column does not add to 95, because the same resistor and capacitor values serve several functions.
Where the time went
Engineering + educationMarketing + business
Estimated, but with high confidence. Tracking system was not yet running.
Codebase size - AI effect
Net lines of source across the firmware, the cloud app and backend, the website and docs, and the iOS app.
Regulator firmwareCloud appCloud backendWebsite and docsiOS app
AI spend, cumulative
Tokens per month
Same time axis as the chart above, so the two line up. The session log only starts 17 June 2026.
Tokens run
Lines added per month
Regulator firmwareCloud appCloud backendWebsite and docsiOS app
Show as a table
| Month | Regulator firmware | Cloud app | Cloud backend | Website and docs | iOS app | Total |
|---|---|---|---|---|---|---|
| 2024-04 | 1,078 | 0 | 0 | 0 | 0 | 1,078 |
| 2024-07 | 1,078 | 0 | 0 | 0 | 0 | 1,078 |
| 2024-10 | 3,084 | 0 | 0 | 0 | 0 | 3,084 |
| 2025-01 | 7,777 | 0 | 0 | 0 | 0 | 7,777 |
| 2025-04 | 4,796 | 0 | 0 | 0 | 0 | 4,796 |
| 2025-07 | 11,166 | 411 | 0 | 0 | 0 | 11,577 |
| 2025-10 | 19,111 | 411 | 0 | 0 | 0 | 19,522 |
| 2026-01 | 25,895 | 7,013 | 0 | 0 | 0 | 32,908 |
| 2026-04 | 47,309 | 7,087 | 2,731 | 27,649 | 0 | 84,776 |
| 2026-07 | 114,302 | 7,551 | 6,265 | 90,371 | 1,599 | 220,088 |
| 2026-08 | 132,591 | 7,492 | 7,471 | 102,401 | 1,691 | 251,646 |
AI Costs
Token retail value
$13,925
Actual spend
$512
Subscription savings
$13,413
AI subscriptions paid, by month
Which plans, over time
Which models ran the work
Tracking this only began 17 June 2026.
Opus 4.8Fable 5Opus 5Sonnet 5Haiku 4.5
Timeline
X Engineering
AI
Mar 2019
X Engineering founded A mechanical engineering consultancy, working on diesel engine development.
Aug 2019
An Arduino starter kit Bought on Amazon.
35 months
Jul 2022
The kit gets opened Ran the blink sketch. Project clock starts here.
8 months
Mar 2023
Parts start arriving Three orders to Marlin P Jones inside two weeks, $535 of components.
AI industry
GPT-4 OpenAI, 14 March 2023.Jun 2023
First regulator prototype A daughter board on a Heart InCharge regulator: digital pot under Arduino control
Sep 2023
Joined The Hardware Academy And met the freelancer who did the early hardware design.
Nov 2023
Second prototype The first breadboard regulator built entirely from basic parts. An H-bridge drove PWM into the alternator field
7 months
Jun 2024
First custom circuit board ordered From PCBWay.
8 months
Feb 2025
X Engineering
First AI subscription ChatGPT, $20, on 16 February 2025. Work moves to copy and paste with a browser LLM.Mar 2025
Boards move to JLCPCB First order, March 2025.
Apr 2025
X Engineering
Claude subscriptionMay 2025
AI industry
Claude Code generally available from Anthropic10 months
Mar 2026
V9 boards ordered
X Engineering
Claude Code adopted, development changes slopeMay 2026
First regulator sold
AI Assisted Measurement Methods
| Money | Copilot tracks all transactions, Claude pulls and classifies expenses weekly. |
| Time | Customized instance of ActivityWatch. |
| Code/Tokens | Standard GitHub workflow makes this one the easiest. |
Last run 26 August 2026.